.container {
  height: 538px;
}
.box_4 {
  border-radius: 20px;
    background-color: lightblue;
    padding: 16px;
    column-rule: 3px groove lightcoral;
    animation: width 5s infinite;
}
@keyframes width {
  50%{
    column-width: 20px;
  }
}